How to export your email to PST file for email migration or backup
In Outlook File tab, choose Options find Advanced and choose Export.
Choose Export to File
Choose Outlook Data File (pst)
Choose top level (whole mailbox) or just what you want to export (for example Inbox or contacts only). Be sure that Include subfolders is selected.
Choose destination to save file and file name.
Click Finish.
On the new computer
Copy this file to USB drive and transfer to new computer. Do not delete email on old computer until you are sure all that you need is on new computer.
Open Outlook and under File tab choose Open, Open Outlook Data File. Note: Another way is to use Import function.
Choose file you created on old computer.
Click OK.
More resources:
http://www.cumc.columbia.edu/it/howto/email/exp.html
http://office.microsoft.com/en-us/support/results.aspx?ctags=CH010371340